1. Field of the Invention
The present invention relates to equipment for material, product, and process testing. More particularly, the present invention finds use in the testing of various printing inks, coatings, pulps, papers and chemicals of the type used by the printing industry. Most particularly, the present invention provides a portable tester for accurately and reliably testing the effects of varying factors such as printing pressures, printing speeds, delay intervals and printing materials.
2. Description of the Prior Art
The need to examine the properties of incoming printing materials has been generally recognized in the printing industry. The high production speeds and large printing formats of modern printing presses make down-time for testing and adjustments an expensive matter. The effective examination and testing of printing materials can provide the data required to set and adjust the printing presses for variations in the materials. Therefore, the need for an accurate and reliable means for testing printing materials prior to their use is desired in order to avoid the loss of production and to maintain the quality of the printed materials has been recognized.
In order to fill the need for testing printing materials, printability testers have been developed. These testers are used to examine printing materials with respect to such variables as ink film thickness, printing pressure, printing speeds and delay intervals which are present during any printing process. Various standardized tests such as dry pick, wet pick, wet repellency, flexographic, gravure, set off, one-color and two-color printing have been used to determine what these variables should be with respect to the various materials in order to achieve the desired results. The printing industry recognizes ISO standards that have been developed and promulgated for some of these tests.
The printability testers in use today still utilize mechanical systems which cannot always meet the requirements for testing modern materials. These testers provide a sector, or common impression cylinder, upon which a test strip of printing paper is mounted. One of two printing disks, coated with a predetermined amount of ink or other print testing material, are applied at a given pressure to the test strip mounted on the sector. The sector is then rotated at a given speed causing the printing disk or disks to print on the test strip. The sector can be rotated at a constant uninterrupted speed, or it can be stopped halfway through its rotation and then continue after a preset time interval. After the sector has rotated a predetermined distance, generally equal to the length of a test strip, a mechanical cam lifts the printing disks off of the sector. The test strip is then removed and examined to determine the effects of various parameters such as speed, printing pressure, and drying time on the materials.
The printing pressure is applied to the disks during testing using hand-adjustable springs which may impart a force of up to 1000 newtons. The disks are manually brought into contact with the sector before the sector drive system is engaged. After the sector rotates a predetermined distance which is less than a full circle, but generally the length of the test strip, a cam lifts the disk or disks from the sector. The cam and drive mechanisms must therefore have sufficient energy to overcome the printing disk spring force.
These prior art testing machines typically weigh more than 250 pounds and are generally powered by large three-phase 380 volt or 440 volt motors. The basic systems are mechanical and require a large flywheel to store the energy required to operate the mechanical systems. In use, the heavy loads cause the tester to vibrate; this results in variations of pressure with which the printing discs are applied during testing.
The existing printability testers are also not user-friendly. In order to mount a test strip on the sector, the operator has to manually turn the sector while it is still loaded by the mechanical system and linkages in the tester. The operator also has to be trained in printability testing and needs to manually set the tester for each different type of test to be performed. All test data must also be manually read from the settings on the machine and recorded by the operator.